Plasticizers are commonly incorporated into polyvinyl chloride (PVC) in order to transform rigid PVC resin into flexible PVC articles. Esters of phthalic acid (phthalates) are used as primary plasticizers at about 10-60 parts per 100 parts (phr) of PVC. Epoxidized vegetable oils, such as epoxidized soybean oil (ESBO) and epoxidized linseed oil (ELSO), are used as secondary plasticizers. Further examples of secondary plasticizers are epoxidized fatty acid mono-esters, such as epoxidized methyl soyate and epoxidized 2-ethylhexyl tallate. Additionally, epoxidized octyl tallate and butyl epoxystearate are used commercially as secondary plasticizers for PVC [a) PVC Handbook by Charles, Wilkes, Charles Daniels, James Summers, Hanser Gardner Publishers; 2005, p.180; and b) Theory and Practice of Vinyl Compounding by Vic Struber; Argus Chemical Corporation; 1968; Library of Congress Catalogue No. 68-19157. pg. 4]. Struber refers to epoxidized 2-ethylhexyl tallate, which is commercially available from Galata Chemicals LLC as Drapex® 4.4. Struber also describes epoxidized octyl oleate, which Galata Chemicals LLC offers as Drapex 3.2. ESBO and ELSO have limited compatibility with PVC due to their high molecular weight, while epoxidized mono-esters are known for their unacceptably high extraction out of the PVC matrix.
Several patents and patent applications relate to bio-based plasticizers derived from fatty acids containing epoxy functional groups, as referred to hereinbelow.
U.S. Pat. No. 2,895,966 describes plasticizer stabilizers for synthetic resins and plastic compositions comprising said plasticizer stabilizers.
U.S. Pat. No. 3,049,504 relates to plasticizer stabilizers for synthetic resins.
U.S. Patent Application No. 2002/0013396 discloses compositions and methods for plasticizing polyvinyl chloride polymers where the plasticizers contain fatty acids derived from vegetable oils and the fatty acids are substantially fully esterified with an alcohol (mono-ol or polyol), the fatty acids having unsaturated bonds that are substantially fully epoxidized, and wherein the fatty acids are added substantially randomly to one or more hydroxyl sites on the alcohol. The plasticizers may be added in amounts between about 10 to 230 phr of PVC resin.
WO2009/102592 describes unhindered polyols used to react with an epoxidized soyate to make epoxidized soyate diester in the presence of a catalyst. The unhindered polyol can be 1,3-propanediol or any polyol having four or more carbon atoms with no two adjacent carbon atoms having hydroxyl functionality. A combination of catalysts is used to promote the trancesterification reaction of the epoxidized soyate with the unhindered polyol to yield a high percentage of epoxidized sovate diester with epoxy functionality retained. The primary catalyst is a metallic hydroxide, and the secondary catalyst is a titanate. Bioderived epoxidized soyate diester plasticizers useful for thermoplastics and thermosets result.
U.S. Patent Application No. 2010/0010126 describes the use of the interesterification reaction between vegetal or animal oils as monoacid esters (preferentially with 1 to 12 carbons) and monoalcohol esters (preferentially with 1 to 12 carbons). The use of ethyl acetate is preferred as it is a product that may be obtained from ethanol (renewable) and has a boiling point (77 deg. C.), which facilitates separation by vacuum distillation at the end of the reaction and its reuse. By varying the molar ratio between glycerol Wester (oil or fat) and monoalcohol ester, different proportions of glycerol esters are obtained with 1 or 2 linked fatty acids and 1 or 2 linked acids of short chain, along with the formation of fatty acid ester and monoalcohol ester. After the distillation of excess residual ethyl acetate, products are obtained with viscosity from 21 to 33 cPs at 25 deg. C., in the case of the reaction with soy oil.
U.S. Patent Application Publication No. 2010/0010127 relates to bioplasticizers or primary oleochemical plasticizers and the improved process for obtaining thereof. It refers primarily to epoxidized oleochemical plasticizers produced from vegetable oils, as substitute for traditional petrochemical plasticizers.
U.S. Pat. No. 7,071,343 describes epoxidized glyceride acetates made by a process which comprises reacting an epoxy fatty acid ester and triacetin.
WO2011/143028 relates to PVC resin-based compositions that include biochemical plasticizers as the primary plasticizers. The compositions include PVC resin, a compatibilizer, one or more biochemical plasticizers and, optionally, a thermoplastic elastomer impact modifier. The biochemical plasticizers are present in substantial quantities in the compositions and, in some embodiments, are the only plasticizers present in the compositions.
Notwithstanding the above literature, there is a continuing need for improved bio-based plasticizers having reduced extraction properties and lower volatility for halogen-containing polymers, such as polyvinyl chloride (PVC) and its co-polymers.